The present invention pertains to a method for activating the immune system of a patient by intermittently administering interleukin-2 (IL-2) to that patient. Such administration of IL-2 can optionally be combined with other therapies, such as anti-retroviral, anti-bacterial or anti-fungal therapies, suitable for treatment of the patient""s condition. This invention also relates to an approach to gene therapy that entails administering IL-2 to a patient so as to facilitate in situ lymphocyte transduction by a retroviral vector also administered to the patient.
Attempts at immune activation and restoration in the past have utilized bone marrow transplantation or lymphocyte transfers (H. C. Lane et al., Ann. Internal Med. 113: 512-19 (1990)), immunomodulating agents such as immuthiol (J. M. Lang et al., Lancet 24: 702-06 (1988)) or isoprinosine (C. Pedersen et al., N. Engl. J. Med. 322: 1757-63 (1990)), and recombinant cytokines such as interferon alpha (IFN-xcex1) and IL-2. H. C. Lane et al., Ann. Intern. Med. 112: 805-11 (1990); H. C. Lane et al., J. Biol. Response Mod. 3, 512-16 (1984); D. H. Schwartz et al., J. Acquir. Immune Defic. Syndr. 4, 11-23 (1991); P. Mazza et al., Eur. J. Haematol. 49: 1-6 (1992); H. W. Murray et al., Am. J. Med. 93: 234 (1992); H. Teppler et al., J. Infect. Dis. 167: 291-98 (1993); P. Volberding et al., AIDS Res. Hum. Retroviruses 3: 115-24 (1987). These studies have resulted in minimal or only transient immune system restoration.
The use of biologic response modifiers in general, and of IL-2 in particular, is an active area of clinical research. Interleukin-2 is a T cell-derived lymphokine with a number of immunomodulating effects including activation, as well as induction of proliferation and differentiation, of both T and B lymphocytes. K. A. Smith, Science 140: 1169-76 (1988). Exogenous IL-2 has been shown in vitro to increase the depressed natural killer cell activity and cytomegalovirus-specific cytotoxicity of peripheral blood mononuclear cells from patients with AIDS, as well as to increase IFN-xcex3 production by lymphocytes from patients with AIDS. A. H. Rook et al., J. Clin. Invest. 72: 398-403 (1983); H. W. Murray et al., loc. cit. 76: 1959-64 (1985).
IL-2 given by high dose infusion has been employed in the treatment of renal cell carcinoma and melanoma. J. Nat""l Cancer Inst. 85(8): 622-32 (1993). For example, doses of 36 million international units (MU) given continuously over a period of 24 hours has been used in the treatment of cancer (18 MU is equivalent to about 1 mg protein). Lancet 340: 241 (1992). The use of high doses of IL-2 generally is not well tolerated by patients, however, and side effects are more pronounced at such high levels.
Subcutaneous administration of IL-2 has been evaluated extensively in patients with metastatic cancer, although most often in conjunction with alpha interferon. Our current data suggest that the maximum tolerated dose of subcutaneous IL-2 given over a five day course of therapy is about 21 MU/day. Most previous trials used a four week regimen of dosing. The highest subcutaneous dose of IL-2 delivered in a single agent setting was delivered in an intrapatient dose escalation trial where four patients tolerated doses equal to or in excess of 24 MU/m2/day. These patients had already received more than one month of IL-2, so these doses were tolerable in spite of chronic dosing. Whitehead et al., Cancer Res 50: 6708 (1990). A similar trial delivered doses in the range of 18 MU/patient on a five day basis followed by lower doses for prolonged periods. Sleijfer et al., J. Clin. Oncol. 10:1119 (1992); Lissoni et al., Eur. J. Cancer 28: 92 (1992). Other trials have used lower dose IL-2 regimens with similar toxicities. Urba et al., Cancer Res. 50: 185 (1990); Stein et al., Br. J. Cancer 63: 275 (1991); Atzpodien et al., Mol. Biother. 2: 18 (1990). Thus, subcutaneous dose levels of IL-2 in the range of 18-24 MU/day have been reasonably well tolerated over one month of therapy.
Subcutaneous IL-2 is poorly absorbed, however, and local reactions can be dose-limiting. McElrath et al., Proc. Nat""l Acad. Sci., USA 87: 5783 (1990), suggest that locally high concentrations of IL-2 can have systemic effects as assessed by activation of lymphocytes remote from the site of injection. Further, in HIV seronegative populations, subcutaneous IL-2 at tolerable doses has led to increases in lymphocyte counts and improved cytotoxicity as assessed by NK and LAK activity. Most of the patients treated with these regimens had metastatic cancer and the additional observation of objective tumor responses suggests that the immune activation was clinically important.
Other researchers are evaluating IL-2 in the treatment of other diseases, including HIV infection. The use of lower doses of IL-2 in a continuous therapy regime has been disclosed by Yarchoan et al., U.S. Pat. No. 5,026,687. More specifically, Yarchoan et al. teach the use of the anti-retroviral agent ddI in combination with IL-2 administered continuously at a dosage between 25,000 to 1 million international units (MU) per day, for a period of three months. While Yarchoan et al. predict that xe2x80x9cbeneficial resultsxe2x80x9d will accompany the combined ddI/IL-2 regimen, they do not attribute these results to IL-2 per se. Moreover, dosages at this lower level have been shown to cause an initial increase in CD4 level that was transient in nature: that is, CD4 levels returned to baseline within 6 months after the completion of the treatment.
Many researchers feel that the use of IL-2 is contraindicated in patients with HIV infection due to its potential to activate HIV. No method of treatment of HIV with IL-2 has been disclosed which results in a sustained response or which yields long-term beneficial results.
Cells that have been stimulated to actively synthesize DNA are susceptible to transduction by gene transfer therapy. Present methods of gene therapy require a complicated, in vitro transformation. More specifically, cells are removed from a patient, activated in vitro, and used to establish cell lines which are then gene-transduced in vitro and re-implanted in the patient. This procedure is expensive, and its success its limited due to the potential of failure at each of the steps of activating the cells, effecting the transduction, and implanting the cells in the patient for expression.
Attempts at using retroviral vectors to effect in vivo gene transfer have been limited. Retroviruses will only integrate stably into target cells that are actively synthesizing DNA. This integration must occur before retroviral gene expression can be effected. Because only a fraction of cells are actively producing DNA at any giving time, such in vivo gene transfer methods have shown little success.
It is therefore an object of the present invention to provide a means for activating and expanding the elements of the immune system that employs IL-2 but that avoids the pronounced side-effects associated with conventional IL-2 treatments.
It is also an object of the present invention to provide a means for treating a wide variety of disease states, including HIV infection, through the use of IL-2 therapy.
It is a further object of the present invention to provide an approach to effecting retroviral vector-mediated transduction in situ, in the context of gene therapy, for a patient whose immune system has been activated by the administration of IL-2.
In accomplishing these and other objects, there is provided, in accordance with one aspect of the present invention, a method for treating a disease state characterized by an immunological impairment, by the intermittent administration of IL-2 wherein IL-2 is administered to the patient in an amount that is sufficient to increase the CD4 count in the patient. In accordance with this method, the IL-2 is administered in a series of administrations effected intermittently, each administration being continuous over a period of time that is sufficient to allow spontaneous DNA synthesis in the patient to increase and peak, and each subsequent administration following the preceding administration in the series by a period of time that is sufficient to allow IL-2 receptor expression in the patient to increase, peak and then decrease to 50% of peak value.
In another aspect of the present invention, the period of time that each subsequent administration follows the preceding administration is sufficient for CD4 counts to increase and then decrease to about 125% of a baseline value.
In accordance with one aspect of the present invention, the IL-2 administration is effected by intermittent continuous infusions, and in accordance with another aspect of the present invention, the administration is effected by an intermittent series of subcutaneous injections, which may be given in one or more injections per day.
In accordance with another aspect of the present invention, a compound (or compounds) which blocks the activity of pro-inflammatory cytokines is administered concomitantly with the IL-2 therapy to minimize the side effects of the IL-2.
In accordance with another aspect of the present invention, the IL-2 therapy is combined with another therapy, such as anti-retroviral therapy, which targets a specific disease state.
Another aspect of the present invention provides a kit for activating the immune system of a patient comprising (i) a liquid preparation comprising an amount of IL-2 in a pharmaceutically acceptable carrier and (ii) instructions on administering the preparation to a patient suffering from an immunological impairment or infectious disease in a series of administrations effected intermittently, such that (A) each administration is continuous over a period of time that is sufficient to allow spontaneous DNA synthesis in the patient to increase and peak, and (B) each subsequent administration follows the preceding administration in the series by a period of time that is sufficient to allow IL-2 receptor expression in the patient to increase, peak and then decrease to 50% of peak value.
Another aspect of the present invention provides a process for modulating the immune system of a patient, comprising the steps of: (A) activating the immune system by the procedure described above, and (B) administering a retroviral vector to the patient to effect in situ transformation of lymphocytes.
Additional objects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages may be realized and obtained by means of the uses and compositions particularly pointed out in the appended claims.